Containment sumps are typically used with subterranean piping systems such as those used at gasoline service stations to move fuel or other liquid chemicals from an underground storage tank to an above-ground dispensing station. Underground storage tanks and the associated piping systems pose serious potential environmental and fire hazards if the fuel or liquid chemicals leak from the tanks and/or the piping systems into the ground.
Operators of such tanks and piping systems are aware of these potential risks and realize that a priority must be given to the planning and construction of the infrastructure if underground storage tanks and piping systems, especially for gasoline service stations. The development of piping systems made of plastic materials have enabled cost-effective and environmentally-friendly alternatives to steel piping systems that can rust and corrode over time.
In gasoline service station installations, the piping systems running between an underground storage tank and the gasoline pumps will typically pass through containment sumps, one located above the storage tank and one located beneath each gasoline pump. The containment sump beneath a gasoline pump is an open-top container with a closed bottom to catch any leaked liquids whereas the containment sump mounted on top of an underground storage tank has both an open top and is mounted directly to the top of the underground storage tank. The top of the tank forms the bottom of the sump. Containment sumps, when viewed from the top, may be square, rectangular, circular, octagonal or any other desired shape. Apertures in the sidewalls of the containment sumps permit pipes to pass through. A common material used in the construction of containment sumps is fibreglass reinforced plastic such as resin or other polymeric materials.
Other precautions taken to overcome environmental risks include a secondary containment system for piping systems from underground storage tanks to gasoline dispensing pumps. This involves each primary fuel supply pipe being placed in a secondary containment pipe that may be sealed at the ends of the field supply and pipeline. The secondary pipes prevent fuel leaking from a primary fuel pipe to escape into the environment and convey any leaking fuel to a remote sensing device. The secondary pipes are separate from the primary pipes and are sleeved over the primary pipes when they are installed between the underground storage tanks and the gasoline pumps.
To prevent the ingress of water into containment sumps through the pipe apertures in the sump sidewalls, it is necessary to seal the junction between the pipe and the sump sidewall. One method used to accomplish this is to attach a fitting or pipe entry boot to a portion of the sump wall around the aperture and to place a rubber “boot” that fits concentrically about the pipe. The boot is clamped to both the pipe and the fitting using, for example, Jubilee™ clips. Some types of fitting are bolted to the sump sidewall where other types comprise inner and outer parts that sandwich the sump sidewall by having the inner and outer parts fastened to each other by a screw-threaded connector that extends through the aperture. These connectors often include a rubber seal located between a portion of the connector and the sump sidewall. Neither of these type of fittings provides a completely effective seal between the pipe and a sump sidewall.
Over time, both types of seals can allow water to leak into the containment sump and accumulate. For containment sumps located on top of an underground storage tank, this makes maintenance of the sump bottom and tank entrance very difficult. In addition to allowing the ingress of water, defective seals between pipes and sump sidewalls can allow gasoline and/or vapours to escape the sump into the environment. It would be preferable if a pipe fitting could be chemically bonded (solvent welded) or electro-fusion welded to both the pipe and the sump sidewall. However, there does not exist a fitting capable of being welded to both plastic pipes and fibreglass-reinforced plastic containment sumps.
It is, therefore, desirable to have a composite laminated sheet material for constructing a containment sump that enables a pipe entry fitting or boot to be welded to both a pipe and the sump sidewall.